Conventional laundry washing machines include a tub, a perforated basket mounted in the tub and an agitator mounted in the basket. Fabrics to be washed are placed in the basket and water and detergent are added to the tub (and thus the basket). The agitator is oscillated to agitate the fabrics and fluid and then the agitator and basket are rotated at high speed to extract the fluid, The process is repeated without detergent to rinse the fabrics.
Conventionally the agitator and basket are driven from an AC electric motor through a transmission. When the rotor of the motor rotates in one direction, the transmission converts the rotary input into a reciprocating or oscillating output drive for the agitator. Such agitator oscillation normally is sinusoidal in form. When the rotor rotates in the other direction, the transmission rotates the agitator and basket together at high speed to extract the liquid. Such transmissions are expensive to build and add considerably to the weight of the washing machine. Also, the agitator oscillation conventionally has been limited to some form of sinusoidal movement, which is an inhibiting factor in most effectively tailoring the wash action to the fabric load.
Multi-speed drives have been used to add some degree of flexibility. One approach utilizes multi-speed motors while another employs multi-speed clutches. While each provides differentiated wash speeds, neither approach changes the basic limitation of one wash motion.
Such agitator machines typically include clutches, mode shifting mechanisms, pulleys and gear mechanisms. Also it often is necessary to offset the motor from the axis of the agitator and transmission which, in turn, requires the addition of a counterweight. All of these kinds of items add to the complexity and cost of such machines.
More recently other approaches have been suggested. One example is U.S. Pat. No. 4,449,079--David M. Erdman, assigned to General Electric Company the assignee of the present invention, which patent is incorporated herein by reference. This patent discloses a laundry machine driven by an electronically commutated D.C. motor such that various agitation wave shapes are possible. The control in the Erdman approach senses motor speed and compares the actual sensed value with a desired value to produce an error signal used in controlling the motor.
An oscillating basket washer does not have a separate agitator for imparting wash energy to the fabrics being washed. Rather vanes or ribs are fabricated as part of or attached to the basket and the basket is oscillated to impart wash energy. No oscillating basket design has proven to be have enduring commercial success and agitator machines have become predominant.